Depreciation Expense on the Heating and Air Conditioning Equipment for the Factory

Depreciation Expense on the Heating and Air Conditioning Equipment for the factory of $50,000 is allocated to five departments.The cost-allocation base for this expense is the number of cubic feet,which equals 100,000 cubic feet.Information for five departments is below:
$\begin{array}{lll} \text {Department }& \text { Square Feet}& \text { Cubic Feet}\\\text { Department A } & 15,000 & 15,000 \\\text { Department B } & 5,000 & 5,000 \\\text { Department C } & 30,000 & 20,000 \\\text { Department D } & 20,000 & 35,000 \\\text { Department E } & 10,000 & 25,000\end{array}$
How much Depreciation Expense is allocated to Department A?

A) $2,500
B) $7,500
C) $15,000
D) $18,750